Threads are a convenient means of joining two or more components in a myriad of applications including industrial, automotive, aerospace, consumer and plumbing, among others. Machining is used to produce the vast majority of mating external and internal threads on metal and ceramic components. Machining is both a costly and time- consuming process for producing threaded components, and in many cases it may represent the costliest step in an entire manufacturing process.
Investment casting represents a net and near-net-shape method for forming threaded components. However, investment casting is generally a time-consuming, multi-step process that is inefficient for the manufacture of parts in high volume. Generally, some finishing operations are required to produce a finished article.
Injection molding is a preferred process for manufacturing complex, net-shape parts from metal and ceramic powders in high volume, and therefore offers considerable advantages over processes that require additional machining and finishing operations. The injection molding process is ideally suited for producing threaded articles that have desired properties without performing additional costly finishing operations.
The present invention provides a method for manufacturing metal and ceramic threaded parts by low pressure injection molding using aqueous feedstocks. More specifically, according to the present invention a process is provided for shaping threaded parts from metal and ceramic powders. The process generally comprises the following steps: introducing into a conventional injection molding machine aqueous feedstock consisting essentially of metal powders, ceramic powders or mixtures thereof, water, a binder from the family of polysaccharides known as agaroids, and optionally other additives to enhance the processability and/or stability of the material; molding the threaded part at low temperature (e.g, approximately 85.degree. C.) and low pressure (e.g., between approximately 400 to 1000 psi hydraulic); cooling the molded part in the mold to a temperature below the gel point of the binder (e.g., approximately 37.degree. C.); removing the cooled, threaded part from the mold; drying the part to remove the water; heating the part to a first elevated temperature to remove the binder, and then to a second elevated temperature to density the part to its final desired condition.